问题 解答题
脱式计算(能简算的用简便方法计算,写出计算过程.)
(1)7.5×2.3-1.9×2.5
(2)(78.6-0.786×25+75%×21.4)×2011÷75
(3)1
1
2
+2
1
6
+3
1
12
+4
1
20
+5
1
30

(4)9.1+9.2+9.3+…10.7+10.8+10.9.
答案

(1)7.5×2.3+1.9×2.5

=17.25+4.75

=22;

(2)(78.6-0.786×25十75%×21.4)×2011÷75,

=(78.6-78.6×0.25+75%×21.4)×2011÷75,

=[(1-0.25)×78.6+0.75×21.4]×2011÷75,

=[0.75×78.6+0.75×21.4]×2011÷75,

=(78.6+21.4)×0.75×2011÷75,

=100×0.75×2011÷75,

=75×2011÷75,

=75÷75×2011,

=2011;

(3)1

1
2
+2
1
6
+3
1
12
+4
1
20
+5
1
30

=(1+2+3+4+5)+(

1
2
+
1
6
+
1
12
+
1
20
+
1
30
),

=15+[(1-

1
2
)+(
1
2
-
1
3
)+(
1
3
-
1
4
)+(
1
4
-
1
5
)],

=15+[1-

1
2
+
1
2
-
1
3
+
1
3
-
1
4
+
1
4
-
1
5
],

=15+

4
5

=15.8;

(4)9.1+9.2+9.3+…10.7+10.8+10.9,

=(9.1+10.9)×9+10.0,

=180+10.0,

=190.

问答题 简答题
问答题 简答题